The structure of the bovine proteolytic enzyme, gamma-chymotrypsin has been regined to 1.9A resolution by techniques currently available to the Section on Molecular Structure. These include difference and differential Fourier analyses. A model of the acid protease from Rhizopus chinensis has been constructed using the Molecular Graphic system at the UNC, Chapel Hill, NC. The sequence of amino acids is only partially known, and a tentative sequence has been assigned based on the electron density map and the known amino acid composition.